The present invention relates to the evacuation and fill of inaccessible cavities and more particularly, to the initial evacuation and filling process of a system using a normally closed access valve to evacuate and fill an otherwise inaccessible part of the system.
The preferred layout of systems such as vehicle braking systems may be such that the assembled system includes closed and inaccessible cavities in its normal state. Braking systems conventionally operate on hydraulic type fluid and are often capable of performing advanced functions such as anti-lock braking and traction control. Vehicle braking systems can also operate in introducing moments into the vehicle body as part of a stability enhancement system. Such advanced function braking systems generally incorporate components such as valves, pumps and accumulators which are interposed in the system and interact between the conventional master cylinder and wheel brake actuator. The introduction of these types of components to provide the selected braking functions of the braking system tend to complicate the initial fluid fill processes at the vehicle assembly plant. The components are generally assembled in a module and shipped to a vehicle assembly plant for incorporation into the remainder of a braking system.
With basic vehicle braking systems wherein the brake lines remain continuously open between the master cylinder and all parts of the system it is assured that fluid introduction into the assembled system at the master cylinder assembly can be accomplished without leaving unfilled segments. This becomes increasingly more difficult to achieve when the complexity of the system is increased and the number of components contained therein is multiplied. When system complexity results in effectively inaccessible segments from the master cylinder with the system deenergized, valves must be energized and actuated to completely fill the system from the master cylinder. This is generally considered undesirable in a fast paced assembly environment.
A known method of overcoming this problem, is to prefill the brake modulator with fluid during its assembly. The fluid filled modulator is then shipped to the vehicle assembly plant for assembly into the vehicle. This solution is less than desirable however, since the modulator requires open connection points for assembly to the braking system. A risk is created of fluid leaks during handling, which is particularly problematic since brake fluid is detrimental to painted surfaces such as those found on vehicle bodies.